Wednesday, February 15, 2012

Introduction to Lost Wax Casting by Randall Zadar

The "Lost Wax" method of casting is a refinement of a very old and ancient process dating back some two thousand years. Our ancient ancestors discovered that molten metal from a volcano, when cooled, assumed the exact shape of the clay or stone it flowed upon. This discovery led many of our early ancestors to produce simple molds in sand, stone or clay. They would pour in molten metal and produce ornaments or tools.

Later, jewelers such as the great Karl Faberge used Lost Wax Casting to produce some of the most beautiful and complex jewelry ever made. In the early 1900's, dentists began to use the process to restore the exact shape of a damaged tooth. In the 1930's, the manufacturing jewelers in this country discovered that they could use the same process to produce jewelry. Today, the process has been refined and is widely used by industry to produce complex parts.

The artist has also benefited from the process. Who can forget the magnificent bronze sculptures by Frederick Remington or Auguste Rodin? Sculptors all around the world soon realized the potential of this casting process to produce art.

As a sculptor of miniature art, I find the Lost Wax Casting process a perfect medium for my artistic expression. The process allows for very intricately cast designs. I then hand-paint each one in oil paints. The average size of my work is under an inch in height.

The following is a description of the steps I take to produce my figurines. The master for every figurine is first painstakingly sculpted out of wax. I use the process of building up the wax and then sculpting out the design. I use a combination of soft and hard wax to sculpt the master; the soft wax is good for building up and allows the figurines to have a bit of flexibility when carved. The hard wax is rigid and holds the extreme detail required.

The tools I use are basic. A specially sharpened X-Acto Knife, a spade shaped blade and some pins. I also use files for shaping the wax and a Q-Tip for smoothing the wax. For melting and building up, I use an electronically controlled heating tool.

After the wax master in completed, I cast it in sterling silver. The process basically consists of mounting the wax in a metal flask. A plaster type material call "Investment" is mixed with water, vacuumed to remove air, then poured into the flask. After the investment hardens, the flask is placed in an oven and slowly heated to 1,350 degrees. The wax melts out and becomes "lost". This leaves a cavity in the investment in the exact shape of the wax pattern. Molten sterling metal is forced into the mold cavity using centrifugal force or poured in using a vacuum assist. After cooling down, the metal is broken from the mold by quenching it in water. The new casting is now ready for finishing operations.

The new sterling master is cleaned, inspected, and prepared for use in the production mold. The production mold is used to produce additional wax patterns for casting. This mold is made from strips of un-cured rubber. These strips of rubber are packed around the sterling master and placed inside a metal frame. The mold is placed inside a vulcanizer, which uses heat and pressure to cure the rubber.

After the mold is vulcanized, it can be cut open. Using surgical blades, the mold is cut open with a choppy cutting motion. This cutting motion allows the mold to lock back together when injecting a wax pattern. Release cuts are made to allow the removal of the delicate wax patterns. Also, vent cuts are made which allow the air to escape as the wax enters the mold.

Once the rubber mold is made, wax injection begins. A wax injector, which melts the wax and injects it under air pressure, is used. The molten wax flows into the mold and then cools for several minutes. When cooled, the mold can be carefully opened to remove the new wax pattern. Not every pattern is useable. Generally, seven or eight out of ten are good.

The wax patterns are now mounted inside a flask and the casting process is repeated as mentioned above. Instead of using sterling silver, bronze metal is used in all the production pieces. The bronze is strong and durable.

The newly cast bronze figurines are now cleaned and prepared for paint. The sprues are cut off each figurine. A sprue is the passageway for the wax to melt out and the metal to flow in. They also anchor the wax pattern inside the flask. Using hand files and rotary tools, any mold lines are removed. Each cleaned figurine is mounted onto a painting stick and given a white base coat using an airbrush. Oil paints are mixed for each color needed and the painting process begins. Once all the painting steps are completed, the figurine is allowed to dry and then varnished.

From the beginning to the end, each figurine must pass through a series of complex steps. The Lost Wax Process is the only way for me to produce the precision detail required for this unique art form.

Discovered from primal forces in nature, this ancient process in theory has not changed. It has been developed to an exact science with sophisticated tools and equipment, but the basic concept is the same and will never change. This leaves us with an ingenious way of transforming delicate wax into permanent metal. The beauty of this process is the ability to cast unlimited designs. The only limitation is our imagination.

Randall Zadar/Sculptor. To learn more about Zadar Miniatures, please visit: